Supervisory and Control Equipment for Audio-Frequency Amplifiers

This paper is divided into two parts: In the first part a new type of level indicator is presented, and in the second a device for controlling the output signal of an amplifier is described. Part I: Two types of level indicators in use at the present time on audio-frequency amplifiers are the r-m-s voltmeter and the average voltmeter. Neither of these will tell the operator how near the signal is to the overload point of the amplifier. A new type peak voltmeter is described that makes continuous measurements of the highest peak values attained by the signal. Part II: An automatic control circuit is described which reduces the amplification of a special amplifier when the output voltage reaches a certain amount, thereby keeping the subsequent equipment from being overloaded.